Such a method is known from Japanese patent publication JP2017921.
In the known method a seed is injected into a cyclonic fluid separator in which the fluid is accelerated to a supersonic velocity and thereby cooled to cause condensation and/or solidification of one or more components of a substantially gaseous multicomponent fluid mixture. The seed is injected downstream of a throat portion of the acceleration section to promote nucleation of large liquid droplets and/or solid particles in the fluid stream, in which a swirling motion is generated to initiate separation of a primary condensables depleted stream from a secondary condensables enriched stream by centrifugal forces.
In the known method the seed is recovered by a method of sedimentation, which indicated that the seed comprises a powder of solid particles. The method does not specify the composition of these particles.
The method according to the preamble of claim 1 is known from U.S. Pat. No. 4,141,701. In the known method a polluted air stream is accelerated to a supersonic velocity and water droplets are sprayed into the accelerated air stream to remove the pollutants.
German patent application No. DE 10040015 discloses the use of droplets comprising a surface active agent to remove pollutants from a gas.
In some embodiments the present invention provides a method wherein a spray is injected into the supersonic fluid stream, which spray comprises solid or liquid particles and/or droplets having a composition and/or electrical polarity which further enhances the separation efficiency of a supersonic fluid separator.